XRT7250 Datasheet, PDF (203/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250 DS3/E3 FRAMER IC
REV. 1.1.1
áç
FIGURE 74. BEHAVIOR OF THE RXPOS, RXNEG AND RXLINECLK SIGNALS DURING DATA RECEPTION OF UNIPOLAR
DATA
Data _{1 0 1 1 0 0 1 0 0 1 1 1 0 1 0 1 0 0 1}
RxPOS
1 10
01
RxNEG
RxLineClk
The user can configure the Receive DS3 LIU Inter-
face block to operate in either the Unipolar or the Bi-
polar Mode by writing the appropriate data to the I/O
Control Register, as depicted below.
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
Disable TxLOC LOC
R/W
RO
1
0
Disable
RxLOC
R/W
1
AMI/ZeroSup*
R/W
0
Table 35 relates the value of this bit-field to the Re-
ceive DS3 LIU Interface Input Mode.
BIT 3
Unipolar/
Bipolar*
R/W
0
BIT2
TxLine CLK
Invert
R/W
0
BIT 1
RxLine CLK
Invert
R/W
0
BIT 0
Reframe
R/W
0
TABLE 35: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 3
0
1
RECEIVE DS3 LIU INTERFACE INPUT MODE
.Bipolar Mode (Dual Rail): AMI or B3ZS Line Codes are Transmitted and Received.
Unipolar Mode (Single Rail) Mode of transmission and reception of DS3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the Transmit DS3 Framer
Line Interface Output Mode
4.3.1.2 Bipolar Decoding
If the Receive DS3 LIU Interface block is operating in
the Bipolar Mode, then it will receive the DS3 data
pulses via both the RxPOS, RxNEG, and the RxLi-
neClk input pins. Figure 75 presents a circuit dia-
gram illustrating how the Receive DS3 LIU Interface
block interfaces to the Line Interface Unit while the
Framer is operating in Bipolar mode. The Receive
DS3 LIU Interface block can be configured to decode
the incoming data from either the AMI or B3ZS line
codes.
184